Conventional sealing devices include one described in JP 4-93571 U (Patent Document 1).
The sealing device is located between an inner race and an outer race of a rolling bearing for a wheel. The sealing device has a metal core, an elastic member fixed to the metal core, a slinger of L-shaped cross section, and a garter spring. The slinger consists of an axially-extending portion and a radially extending portion, and the elastic member has a radial lip which always slides on the axially-extending portion, a first axial lip which always slides on the radially extending portion, and a second axial lip which is positioned radially inside the first axial lip and slides on the radially extending portion. The second axial lip has an annular groove on a radially outer surface.
The garter spring has been inserted in the annular groove of the second axial lip. The garter spring urges or presses the second axial lip radially inward.
In the sealing device, the second axial lip is not in contact with the axially-extending portion while the second axial lip is in a non-worn state, and once the second axial lip becomes worn and the pressing force against the radially extending portion of the second axial lip becomes a predetermined force or less, part of a portion facing the axially-extending portion of the second axial lip comes into contact with the axially-extending portion and constitutes a radial seal.
The second axial lip in its non-worn state functions as an axial seal, while part of the portion facing the axially-extending portion of the second axial lip in its worn state functions as a radial seal. In this way, the sealing device is able to maintain a continuing stable seal function.
Against this background, there has been a demand for a significant reduction in the torque of a sealing device which seals rolling elements of a rolling bearing for a wheel from the outside. The conventional sealing device has a problem that the life of the second axial lip is short.
Patent Document 1: JP 4-93571 U (FIG. 1)